Engine Questions

aweimer · Post by **aweimer** » Fri Jun 18, 2010 9:56 pm

I have a 1975 36' Tri-Cabin. It has Twin Mercruiser 255HP 350cid engines.

Does anyone have any specs on these engines such as WOT RPM and if present the REV limiter (Redline)? I have search the internet and found 4200 WOT and 4500 MAX. I figured someone here would know for sure on a 255HP 350cid Merc.

The reason i ask is that i have props that are too large on the boat. Right now i only get ~3600 WOT which i feel is a little hard on the engines. I had the unfortunate luck of hitting a submerged log in the channel over the holiday, the props are being re-worked. I'm going to have them knock a couple degrees of pitch off to bring up the RPM a bit.

Thanks much.

Aaron.

prowlersfish · Post by **prowlersfish** » Fri Jun 18, 2010 10:44 pm

If I remember correctly the max rpm is 4000-4400 they gave a pretty wide range , the 255 hp was a 351 (ford) not a 350 (chevy) The chevy would be 260 hp 4200-4600 rpm ,

k9th · Post by **k9th** » Sat Jun 19, 2010 8:34 am

I have the same engines in my '79 tri-cabin and the owner's manual lists all of that information. Mine is aboard the boat and I will not be there until next weekend. I can send you the info then if you can wait. I can also scan that information and email it to you if you like.

aweimer · Post by **aweimer** » Sat Jun 19, 2010 12:57 pm

k9th wrote:I have the same engines in my '79 tri-cabin and the owner's manual lists all of that information. Mine is aboard the boat and I will not be there until next weekend. I can send you the info then if you can wait. I can also scan that information and email it to you if you like.

That would be great. I do see now they are 351's sorry, typo there. I didn't get anything related to the engines from the previous owner.

Thanks much!

k9th · Post by **k9th** » Sat Jun 19, 2010 6:39 pm

If you want a copy of my entire owner's manual I will scan it for you and email it. It will be in pdf format.

Where in the Chicago area are you docked? I get over there from time-to-time.

prowlersfish · Post by **prowlersfish** » Sat Jun 19, 2010 9:47 pm

My marine power book says the 351 max rpm is 4400 rpm so I would prop it to around 4200

aweimer · Post by **aweimer** » Mon Jun 21, 2010 6:31 pm

k9th wrote:If you want a copy of my entire owner's manual I will scan it for you and email it. It will be in pdf format.

Where in the Chicago area are you docked? I get over there from time-to-time.

I live in Chicago, dock the boat out with with other family members in Curtice Ohio, Anchor Point Marina.

Thanks so much, i look forward to the data coming my way.

Also thanks for the Max RPM info Prowlerfish, i was thinking 4000-4200 was a good spot.

Stripermann2 · Post by **Stripermann2** » Mon Jun 21, 2010 6:56 pm

My Trojan manual states 4,000 rpm is max for your vessel and engine.

aweimer · Post by **aweimer** » Tue Jun 22, 2010 8:40 pm

Anyone know the gear ratio on the 1975 36 tri cabin?

I'm trying to look at purchasing new wheels for her but i don't have any information on the gear ratio. Would this be on the velvet drive (trans) or the V drive? I've heard 1:1, 1:1.5 and 1:1.9.

I can tell you that i have 21x20 non-cupped props on her now, the prop repair company is working on them now. I have asked them to knock them down in pitch as much as possible since i'm at about 3500-3600 WOT right now and it should be ~4000. I doubt they will be able to get much more out of them.

I was just curious the gear ratio and i can use the handy prop calculator on michigan wheels website. Thanks much.

g36 · Post by **g36** » Wed Jun 23, 2010 6:44 am

if a velvet drive the following links should give you all the info you need to locate the id tag.

http://www.marinemechanic.com/site/page109.html
http://www.correctcraftfan.com/download ... Manual.pdf