5m Humber Destroyer and Yam F70 Combo

[demondesmond]

Anyone out there in Ribland run the above set up? I currently have a 5m Destroyer with a 60HP Etec which is great but lacks a bit of top end speed. I am considering various options but to stay within the recommended transom wieght limit of 135Kg the only other new option to improve top end is the Yam F70. I believe that the hole shot would suffer and that the top end speed would only increase by 3 or 4 kts so could be an expensive trial! I'm hoping someone out there has this set up and can tell me what sort of perfomance they get. Thanks for any info
Des

[njensen]

check out etecownersgroup.com
you'll find lots of threads about propping your E-Tec

[kerny]

Originally Posted by njensen

check out etecownersgroup.com
you'll find lots of threads about propping your E-Tec

Seconded

[demondesmond]

Cheers mate.......I spend a fair bit of time on ETECOwners checking stuff out. It's a great forum for ETEC info. My 60HP is now prop'd correctly (after a fair bit of raising and lowering and trying different ally and SS props.....). I'm just lacking some horses I think so 90 is the way to go

[Markyboyo]

Just out of interest what height/hole did you choose to go for in the end? I'm about to experiment with raising my engine a little.

[demondesmond]

Hello mate. The boat came with my 60HP fitted second hole up from the bottom (17 pitch ally prop) giving me 5400rpm WOT (should be 5750rpm). This gave me 30Kts flat out but struggled to plane (2up). After reading Etecowners and talking to my mate with his 115Etec I raised the engine to the bottom hole (still 17 pitch) and this gave me more revs (about 5650) but was even worse to plane. Dropped the engine back to second hole from the bottom and fitted a 15 pitch ally prop result was 5750rpm WOT, fast onto the plane but top end speed drop'd to 28 / 29kts. I then borrowed a SS 17 pitch (still on 2nd hole up) and that gave me roughly the same performance as my 15 pitch ally but about 5900rpm WOT. I then lifted the engine back to the bottom hole and fitted a 19 pitch SS. Got the revs with this but didn't want to plane at all and the day turned nasty coming back across Morecambe bay which meant an interesting trip back. Anyway I'm back to my 15 pitch ally second hole up and a desire for a bigger engine. Attached are few (crap) pics of where the cav plate sits in relation to the bottom of the keel. This seems to be the best I can get out of my 60HP.
Des

[Markyboyo]

Thanks for the info mate, I'm currently running how it came from the dealer which is approx 1/2 a hole up from as low as it can go on the transom. They fitted 6 bolts meaning any adjustment is going to be a major pain in the arse! I've even considered fitting a jack plate to overcome the 6 bolts. The pic I attached shows what I mean, pretty hard to go up/down from here without re-drilling the transom

It is certainly too low at the moment as the cav plate is well below the water when cruising at say 25 knts. Is yours on the surface as per the E-Tec forum Pics?

I would think I could come higher than you are at the moment, I'm running a 19" viper which can run pretty high before loosing grip and I also have a load more weight aft that should be sinking the stern a bit. Raising it should help lower the bow a little too.

Mark

[demondesmond]

All sounds like solid logic. Just asked my mate how many bolts hold his 115Etec on and he only has 4. No problems with that as far as I know but KWIL is the man to ask. Six bolts aside....raising or lowering was pretty easy. Just supported the skeg on some blocks of wood, removed the 2 hole'd bolts, loosend the 2 slot bolts enough to allow the engine to slide and used the trailer jockey wheel to raise or lower the front of the boat /trailer to get the right height. Pushed the bolts back though with a squirt of sealant and tightend it all back up again.
My cav plate runs just breaking the surface which produces a lot of spray. I think that I could do with a half hole higher but as I am not willing to drill more holes in the transom it will have to do. Even if it was a perfect set up I don't think I'd be able to squeeze another 8 / 10 kts out of it.

Des

[Markyboyo]

4 is defo the normal number of bolts to install an engine. Its pretty much impossible to to trial different engine heights with 6 and I haven't seen another with 6. I'm about 4 knots down on where I should be and hope I will recover a bit of that by raising the motor. Currently looking online at hiring an engine crane so I can sort it out one weekend.......finding the time is hard these days.

Seems strange that you gained 150rpm going from a 15" alloy to a 17" stainless. I would have thought you would have dropped a few hundred rpm at least doing that. Couple of hundred for higher pitch and a few more due to the stainless blades deflecting less under load.

I'd agree that you are going about as fast as you are going to get with the 60 on there.

[demondesmond]

The decision to put the 19 pitch on at the bottom hole was based on the WOT revs of the 17 pitch SS being toward the 6000 limit and the experience of the ally props (higher the engine the faster the prop spun at WOT).
The position of the cav plate was also a factor when myself and Kwil did the runs. It appeared as if the plate was digging in at the front (causing the spray) and we thought it may be causing additional drag. We thought the higher the engine the less drag. The performance didn't bear this out. Of course having one of us stood looking over the transom rather than sat on the back jockey could have influenced things. I think the 17 pitch SS was a viper and the 19 a Solas. No doubt Kwil will correct me if I'm wrong? My experience says the SS spin faster than the same pitch ally props.

[captnjack]

Changing prop brands has made as much as 2" or more in pitch to me (Yam F60). Blade area and/or small changes in diameter is ALOT more important than any of the pitch calculators would have you believe.

The 6 bolts is rediculous, you could remove the middle ones on each side and fill those holes, then raise the engine.

[spartacus]

Coachrib has the new Yammie 70hp (jammy dodger ) on his XS 5.3. http://www.rib.net/forum/attachment....0&d=1322159397

[demondesmond]

I did wonder about various makes of prop and the differences.........I guess with SS being the more 'business' end of the market it could make quite a difference. Thanks for the info captnjack.

Is coachrib about? and can he / she answer any of the above questions (substitute XS for Destroyer.....)

Thanks