Redbay 7.4 / Yamaha ME420sti - HydraDrive

[alt]

Hi all,
Friend in the local club has just landed with one of these and has a few questions, thought i'd try to assist.

I know little about this block (apart from it's a cousin of the Landcruiser 4.2) / out-drive.

First thing I had him do was replace the gear-oil / clean the gauze on the out-drive.

1) Suspect he has the wrong prop fitted. Came with a SOLAS 3511-143-21 which appears to be 14/3" 21" - it just felt wrong

2) Any idea of WOT RPM on this engine? We got 3400RPM @ 45km/h

3) Oil spitting out the dip-stick and crank (front) seal, but the breather is not blocked. Apparently someone else local to us had similar issues (waiting to hear back from him). Turns out the dip-stick is broken (new one on order). Regarding the crank seal... if it is gone, does anyone know if this engine is a timing belt or chain? (If chain at rear of engine, would make changing crank seal a lot easier)

4) I'm a Volvo KAD person but always showed interest in these engines (Another cousin of the Yanmar?) but my knowledge of the engine / out-drive is very limited... any idea of a source for even general owners manual> (boat came with nothing).

[willk]

«HYDRA-DRIVE» DIESEL STERN DRIVE BLACK STAINLESS STEEL PROPELLER
Drive Model Part Number Diameter Pitch Blade Hub Rotation Remark
Single propeller, right-hand rotation
# Dia Pitch #blades Rot
6U3-45971-00-00 18" 13 3 WR RH
6U3-45973-00-00 17.5" 15 3 WR RH
6U3-45975-00-00 17" 17 3 WR RH
6U3-45977-00-00 16+3/4" 19 3 WR RH
6U3-45979-00-00 16+3/8" 21 3 WR RH

Timing belt.

27kts seems a bit light - is it an open boat or a "heavy"?

[beamishken]

Originally Posted by alt

Hi all,

Friend in the local club has just landed with one of these and has a few questions, thought i'd try to assist.



I know little about this block (apart from it's a cousin of the Landcruiser 4.2) / out-drive.



First thing I had him do was replace the gear-oil / clean the gauze on the out-drive.



1) Suspect he has the wrong prop fitted. Came with a SOLAS 3511-143-21 which appears to be 14/3" 21" - it just felt wrong



2) Any idea of WOT RPM on this engine? We got 3400RPM @ 45km/h



3) Oil spitting out the dip-stick and crank (front) seal, but the breather is not blocked. Apparently someone else local to us had similar issues (waiting to hear back from him). Turns out the dip-stick is broken (new one on order). Regarding the crank seal... if it is gone, does anyone know if this engine is a timing belt or chain? (If chain at rear of engine, would make changing crank seal a lot easier)



4) I'm a Volvo KAD person but always showed interest in these engines (Another cousin of the Yanmar?) but my knowledge of the engine / out-drive is very limited... any idea of a source for even general owners manual> (boat came with nothing).

Should make close to 4000rpm lightly loaded & max rated to 3800 with 3600 max continuous rating. Front crank seal isnt hard to do once you get the crank pulley bolt loose 600nm torque iirc & fecking tight with a little corrosion thrown in for good measure. It has a timing belt but its gear driven to the pump & cam drives via toothed belt from the front of the pump. Belt is a doddle to change & destroys the engine if it snaps so cheap insurance if no history.
Gaskets belts filters & seals starter & alternator etc are all landcruiser stuff so easily sourced from local parts shop but easier if you have a landcruiser registration no handy. I can give you a landcruiser reg to use its a 24v version so on your 12v engine the timing belt will be different, you need a reg from an early hdj80 to get the correct belt almost everything else is the same as my hdj100 series

[GuyC]

If you go on the Roughtrax website, it lets you pick a 12V 80.

https://www.roughtrax4x4.com/parts/l...80-90-94-parts

[alt]

Thanks very much for all the advice.

[Ribgalway]

Hi there

I am looking at a rib with this exact engine.
How did you get on? This is a 8.5m rib but only does 18/19 knots which seems grossly slow for the power of this engine. Please let me know if you learned anything

[paulbrown22]

Originally Posted by Ribgalway

Hi there

I am looking at a rib with this exact engine.
How did you get on? This is a 8.5m rib but only does 18/19 knots which seems grossly slow for the power of this engine. Please let me know if you learned anything

Is the turbo spooling up properly on your boat, what kind of WOT are you getting? Slightly more powerful, but I used to run a not dissimilar Toyota 1HD-based Yanmar 6LP 315hp on my 9m Ribtec. That would top out at 40kn and would cruise at 25kn all day at ~2900RPM

[smallribber]

Old Fred here is over 3 years old

[beamishken]

Originally Posted by Ribgalway

Hi there

I am looking at a rib with this exact engine.
How did you get on? This is a 8.5m rib but only does 18/19 knots which seems grossly slow for the power of this engine. Please let me know if you learned anything

My pal has the same 8.4 redbay with the full canopy & he gets 32kts with no passengers @3800rpm his usual cruise speed is 19kts @2500rpm. Definitely something wrong with that boat.

[Ribgalway]

Originally Posted by paulbrown22

Is the turbo spooling up properly on your boat, what kind of WOT are you getting? Slightly more powerful, but I used to run a not dissimilar Toyota 1HD-based Yanmar 6LP 315hp on my 9m Ribtec. That would top out at 40kn and would cruise at 25kn all day at ~2900RPM

Oh that’s very impressive. Turns out I was wron. I’m getting 32 knots which is not too bad. Need to get rev meter working so not sure what rpm.
Do you know if they are easily tuned? Like turning up fuel pump?

[paulbrown22]

Originally Posted by Ribgalway

Oh that’s very impressive. Turns out I was wron. I’m getting 32 knots which is not too bad. Need to get rev meter working so not sure what rpm.
Do you know if they are easily tuned? Like turning up fuel pump?

That sounds far more reasonable and about right for that boat/engine combination, I doubt you'll get much more top end from it.

I wouldn't bother trying to tweak the fuel injection pump - the fuel pumps on these are already completely different from the Toyota original to get more power (along with different turbo, piston changes, etc.), and I've heard too many nasty stories of people with 6LP's trying to alter that and ending up with a disaster on their hands.

If you want a solidly built 8.5m RIB to go faster, you need a bigger engine! Even something like a Yanmar 6LP 315hp is only rated to run at WOT for 5% of the time though (i.e. 30 mins every 10 hours), so I never blast mine around at 40kn everywhere - 25-30kn was very comfortable and easy on the engine.

[Ribgalway]

Originally Posted by paulbrown22

That sounds far more reasonable and about right for that boat/engine combination, I doubt you'll get much more top end from it.

I wouldn't bother trying to tweak the fuel injection pump - the fuel pumps on these are already completely different from the Toyota original to get more power (along with different turbo, piston changes, etc.), and I've heard too many nasty stories of people with 6LP's trying to alter that and ending up with a disaster on their hands.

If you want a solidly built 8.5m RIB to go faster, you need a bigger engine! Even something like a Yanmar 6LP 315hp is only rated to run at WOT for 5% of the time though (i.e. 30 mins every 10 hours), so I never blast mine around at 40kn everywhere - 25-30kn was very comfortable and easy on the engine.

Ah okay I’m used to powerful outboards. Different thing I suppose. How do you find the sterndrive, have you had an issues and have you any advice as I hear very mixed opinions

[paulbrown22]

Originally Posted by Ribgalway

Ah okay I’m used to powerful outboards. Different thing I suppose. How do you find the sterndrive, have you had an issues and have you any advice as I hear very mixed opinions

Presumably on the Yamaha it would have a HydraDrive. My Yanmar had a Mercruiser Bravo 3 which is different and maybe a bit more agricultural in design, but on the plus side much easier to get parts for!

Personally unless someone else knows better I'd be hesitant to spend too much on a boat with a Yamaha/HydraDrive combo, as my understanding is that parts are getting very hard to find given they've been out of production for years now.

I loved my Yanmar 6lp/Bravo 3 combo and only sold when a baby arrived as it wasn't exactly family friendly - an amazing setup on a big RIB that did many thousands of miles without missing a beat. But all outdrives are very maintenance intensive and can be very expensive unless you do some/all of the work yourself. You need to ensure maintenance is done properly otherwise there's a very large hole in the back of your boat below the waterline... You can't lift the outdrive completely out of the water unlike an outboard, so it's constantly underwater being attacked and any leaking seals, etc. will cause problems. I'd personally be hesitant about a stern drive for a boat that lives in the water year round, I think there's just too many pitfalls and too much maintenance. I kept my Ribtec on a trailer for most of its life and put it in the water for weeks/months at a time when I wanted it, then pulled it out again. Unless you really do enormous running hours, the cost of maintaining and running a diesel inboard/outdrive combination these days will exceed a modern outboard engine.

[beamishken]

Originally Posted by Ribgalway

Ah okay I’m used to powerful outboards. Different thing I suppose. How do you find the sterndrive, have you had an issues and have you any advice as I hear very mixed opinions

A sterndrive boat will always be higher maintenance than an outboard it's just the nature of the extra complexity. The hydradrive is an excellent drive, more refined & less corrosion prone than mercruiser bravo but parts are expensive & like anything mechanical they can & do go wrong. I've seen just as many totalled merc & Volvo drives as I have Yamaha. Parts availability wont get better as time goes on but most stuff still available just now. If the worst happens & you do total a drive you can mate the engine to a mercruiser bravo 1 2 or 3.
32kts its is bang on performance wise.

[Ribgalway]

Originally Posted by beamishken

A sterndrive boat will always be higher maintenance than an outboard it's just the nature of the extra complexity. The hydradrive is an excellent drive, more refined & less corrosion prone than mercruiser bravo but parts are expensive & like anything mechanical they can & do go wrong. I've seen just as many totalled merc & Volvo drives as I have Yamaha. Parts availability wont get better as time goes on but most stuff still available just now. If the worst happens & you do total a drive you can mate the engine to a mercruiser bravo 1 2 or 3.
32kts its is bang on performance wise.

I purchased the rib. It’s a tornado rib and 9m. Although it does 32 knots can you advise me from memory how your rib felt when you went full throttle from stop. In my case, you feel practically nothing but a sluggish pull for about 15 seconds, you’d barely know you had accelerated. And then of course the turbo kicks in and it’s pretty ok up to 32 knots.

Should it feel this slow off the line?

[paulbrown22]

Originally Posted by Ribgalway

I purchased the rib. It’s a tornado rib and 9m. Although it does 32 knots can you advise me from memory how your rib felt when you went full throttle from stop. In my case, you feel practically nothing but a sluggish pull for about 15 seconds, you’d barely know you had accelerated. And then of course the turbo kicks in and it’s pretty ok up to 32 knots.

Should it feel this slow off the line?

A diesel RIB with that generation engine is certainly a lot slower to pick up than an outboard equivalent. The turbos on these are pretty big and need the revs up before they kick in, then you have loads of power. The same applies when driving in challenging seas - you need to keep the turbo spooled up if you want to be able to apply quick power to escape a bad wave.

[beamishken]

Originally Posted by Ribgalway

I purchased the rib. It’s a tornado rib and 9m. Although it does 32 knots can you advise me from memory how your rib felt when you went full throttle from stop. In my case, you feel practically nothing but a sluggish pull for about 15 seconds, you’d barely know you had accelerated. And then of course the turbo kicks in and it’s pretty ok up to 32 knots.

Should it feel this slow off the line?

I thought it was an 8.4 redbay same as my pals, I must have confused posters but you'd expect similar which is where you are. Did you say the tach isnt working? Need to know what the wot rpm is to determine if propped correctly.
You might thank your lucky stars you have a yamaha not a yanmar both use the same block but the yam uses a smaller diameter turbine which spools up a bit quicker so the yam is generaly quicker to spool up but turbo lag is definitely a thing with them. Only way to improve it is go the volvo route & have supercharger & turbo which eliminates the turbo lag but adds another layer of complexity. The yam & yanmars whilst not perfect make up by their simplicity & robustness