kubcat

I have a Force 3500, which I have been told is an almost identical hull to a late 80's 36 Cigarette. She was originally built as a race boat in Australia but just before completion she became a cruiser. She was fitted with pods and twin V8 Evinrudes. Weighs about 7000 pounds with no fuel. I have owned the boat since 2000 and have been melting pistons on the port engine at no more than 8 hour intervals. New power-heads and 3 different mechanics could not solve the problem, so twin 496HO's are going in with Bravo X drives. I am ready to cut some holes in the transom but have no idea where. I cannot aim at the same prop position as the outboards as they are much closer together than I can mount the 496's. I am in Sydney Australia and am not likely to find anyone here that has experience with this type of boat, although plenty will tell me they do. Any help would be most appreciated.

375stinger

you might wan rethink before you do that, if your only doing it because you are having bad luck with your outboard then you might want to holdup a sec. why do you keep melting pistons? the v8s are good running motors, and if you replaced powerheads then it seems to be something else going on. you cant have the drives that close together without a staggered installation. maybe post a thread in the cigarette owners forum to ask where people mounted their outdrives on their 35-36cigs. good luck

Ted G

iTrader: (1)

Well, first I guess I'd like to know are you melting pistons or just scuffing the sides up real bad? And if scuffing do the V8's have decel enrichment modifications done to them? If you want to get the best info on the V8's go to www.screamandfly.comthere are some very good guys on there including Gordon Montague who is the undisputed V8 guru. Another option might be 2 300x Merc motors on your same brackets-much more reliable and fuel efficient than the v8's. If the boat was built properly for outboards i.e. more stringers and knees built up to the transom, then a complete gutting of the boat and new stringers is likely necessary and you could put the engines anywhere you want-even staggered. But the work involved may be cost prohibitive. First thing to do is measure stringer placement in the back and see if the engines will fit, if it was originally laid for big blocks, you may just have to hang mounts and punch the transom to get going.

GOODT

I would just switch over to the 300XS o/B
from merc racing great unit has sportmaster lower !!!!!!

rdoactive

Check your stringers. You may have some significant mods just to mount I/Os.

kubcat

Thanks for the replies.

I am not interested in outboards for this boat. I race them in the Australian Offshore Series and they are great for lots of horsepower per cubic inch but in this application, I prefer some lazy big blocks. Personal choice. My other boat is a 20ft Bertram that has a pair of small blocks, I couldn't be happier. Also I have 2 brand new big blocks and drives sitting in my garage. I have taken the plunge on the sterndrive route.

There are stringers in the boat and I even have "engine" hatches. The stringers have a plywood floor on top and this area has been used for storage. Unfortunately I will lose my huge beer cooler.

What I would like to know is at what height to mount the engines, I guess the big blocks will be about 35 to 36 inches apart. Any suggestions on X dimension would be most appreciated.

kubcat

1 more thing. The outboard route was chosen pretty late in the construction process and it actually has a steel sub frame to hold the transom as well as some glasswork. I have spoken to the original builder and he advises that this boat was built for big blocks and Arneson surface drives. He no longer builds/fixes boats and is 600 miles away in any event.

kubcat

The pistons are scuffing the sides real bad and some are missing chunks. It only happens on the port engine, even with the new powerheads. The port engine runs counterclockwise. Usually I can salvage the head and just hone the cylinder It has been 6 of the 8 cylinders in the new powerhead. And it always happens near the same bridge - in either direction, perhaps I am backing off, I don't know. I am getting petty good at replacing a piston, I think about an hour and a half last time. What are the decel enrichment modifications?

Ted G

iTrader: (1)

The V8 gearcases don't freewheel on decel like a Merc. So OMC found out that these motors scuff pistons on decel when the throttle is closed and the boat is slowing down due to a lean condition (idle ports don't supply enough fuel). They designed a system that uses a vacuum switch connected to the intake that turns on the cold start solenoid on decel so fuel is squirted in the motor to keep it enriched. Fairly simple, but it might explain why you keep scuffing pistons.

kubcat

That makes so much sense. Probably does not explain why it only happens to the port engine but this is the best lead I have - Thank you.