Yamaha 250 hp compared to Yamaha 300 hp

[wolf]

Well it gets up and goes great anyways with that duo prop set up fantastic bite I only really notice it when I have 4 people and me, its really not a huge concern, its just getting old still the same motor and 1800 hours on still going strong,could probablly get away with another year but its burning a bit of oil so might as well do it now than later!!!!!!
I can tell you after chatting with you a few months back and others on here on the site it made it a lot easier to rethink it....

Im going with like I said a 383 stroker complete rebuild with a 383 crank (brand new) on 350 mains (balanced being sent to langly somewhere) all new con rods.pistons,rings,bearings, etc also going to roller rocker cam and lifters, and case hardend pushrods, new 4 barrel eldelbrock carb. so should be back in business ina bout 3 weeks re and re.
At about 1/6 of cost of and new outboard............ so far LOL

wolf

 

[Doug]

Roy

That engine will be Deadly.

My last boat had a VP DP and it was unreal for getting onto plane so I know what you're saying about the DP.

I like chev engines and have run SBs and BBs for the last 30 + years and now that aftermarket parts (Good parts) for stroker engine are coming out of China you can create a high HP with very little cost.

What type of heads?

I'm running Ported and Polished Dart heads with wolverine SS valve train and purple strip springs with chev rockers on my LT-1. I can get 6700 rpms (I run a SS crank which is BB to hit 7K) without floating. I did run-ebelbrock roller rockers but kept snapping studs. I don't run a RR cam because in my past experiences I had to keep tuning the valve train too much for my liking. RR are probably much better than back when I was running them and I guess I was too picky when I could hear tap tap tap from the valve train.

Only problems I've ever had with my SB is, it has to rev up to make power and there is no gas savings at any RPMs. It likes gas.

I Can't wait to hear your new engine in the morning while I'm gearing up. I'll come over and take a look.

Al tells me he's installing a new stroker also.

 

[Gunsmith]

Hey Doug , for sure you would not have liked the old solid lifters like I had on my 65 shelby GT 350!

 

[wolf]

Going with the roller rockers with the new cam he puts in (machinist) I did hear him say dart so maybe thats it this guy has built "too many to know" as thats what he told me came highly recommended from a few in the "KNOW"LOL
he has the machine shop right there and he grinds,set,and bores out the vallys etc etc.as well to allow more flow all the ones he has done come in dynoed at 400 to 425 hp so me thinks it will be a great engine.
I do know it is not chev rollers it is a different brand he uses and trusts I saw they were either prple or blue in colour??? lots of info to know LOL LOL
looking forward to it . And yes Al is getting the same guy doing one for him once I take my engine out going to give Him mine and ill take his old one. as ill have my out this week sometime.
It wont be as loud as im going to fabricate a S.S. pipe to fit over the open exhaust out of the back of the boat to dip in the water about 3 inches as its just too loud at the dock LOL LOL but will be loud on plane passing you LOL LOL LOL.

Thanks again for all your info

Wolf

 

[hooktender68]

Keep everyone posted on how the new light V6 does compared to the old heavy one as time goes on. I am interested on how Yamaha does in that department. Cheers

 

[Doug]

The Yamaha 300 is still working well, thats as long as you don't hit anything.
With the new 300 hp I'm still burning about 3+- gallons less than the 250 hp was burning cruising at 30+- mph.

 

[Halilogger]

Was your boat rated for up to 300hp ? Mine is rated for 250hp, but it seems silly not to go for a lighter engine with more ponies.

 

[Doug]

The ISO registration shows the boat can have a 300hp. When I applied for my TC certification for this year I had to submit the change in power so I had to submit the ISO info and it said 300hp.

What year and type of Orca do you have? Do you have the ISO for you boat? it makes life so easy having the ISO info when your dealing with TC.

 

[Halilogger]

It's actually 2004 Kingfisher 2525 I will check what tag I have.......

 

[spring fever]

Hey Doug-just got back from Arizona and enjoyed hearing of your new 300. I was especially glad to hear of the fuel savings-I need all the help I can get to convince the better half that this is a needed upgrade. Saving my pennies and hoping for next year-it would be a significant performance enhancer over my 225. Keep us updated as you get more hours on

 

[wolf]

Well she is finally tinkered enough LOL
Doug tried 3 different props the normal B4 alum i had went up to 4700 rpm top speed almost 40 mph. then tried B5 alum went down to 4100 rpm and top speed was 36 mph so tweeks the B4s and put a cup on the rear prop got it to 4400 rpm wher I want and top was again almost 40 mph.
THEN got a set of C4 Stainless props and being heavy as hell figured it may drop it down some and definatlly did sea trial yesterday was 4450 Rpm and top speed was 40 mph so thats what im sticking too as ive always wanted SS as for fuel dont have it pinned down yet from all the testing but looks to be about the 8 to 9 GPH so far will let you know after thes set of hali tides

wolf