1988 88hp spl conversion to 115

[jkrswld1]

Hey Guys
I've got an Evinrude 1988 88hp spl on a 1977 21ft Marquis that has been converted from an I/O to an outboard rig with the mount box that fits on the stern where the sterndrive was. Curently running a 14x11pitch prop. just not enough motor. I was wondering if it would be feisible to stroke this engine to 115 or larger. Also this engine has only around 50 hrs. on a new power head due to someone that didn't know you had to premix gas on these 88's. But it has since been in storage for the last 4 yrs. I have put new plugs and wires on it and new water pump. Engine starts and idles fine but if you idle any length of time when you go to take off it won't open up. You can shut engine off and restart and take off and it opens up, then when you slow back down it runs rough. I'm thinking carbs. Any other sugesstions?
Thanks

PS. I really enjoy this site seems like a great bunch on here. Got my info on droping lower unit here that went well, peice of cake. Thanks so much for all the info.

 

[emdsapmgr]

Re: 1988 88hp spl conversion to 115

You could put a set of 1 5/16" large bore carbs and high compression heads on it. The only optional pistons are the .030 oversize, which don't add many cubic inches. Even with doing these, you may not be happy with the outcome. That sterndrive boat is a heavy one for 99.6 cubic inches to lug around. If it runs fine sometimes, the carbs may be ok. Could be an ignition problem-they tend to cause more problems when they warm up. Do you have a horn going off? If that engine overheats, it will limit engine rpm's to 2500 till the overheat issue is resolve, or the engine is restarted- when the overheat cycle begins again.

 

[tashasdaddy]

Re: 1988 88hp spl conversion to 115

you are stil going to be under powered, even with the conversion.

 

[Dhadley]

Re: 1988 88hp spl conversion to 115

Since it's been in storage for 4 years I'd suggest starting with cleaning the carbs. If you have some plugged passages you'll be not only starving a piston for gas but oil too. On the other hand if it does scuff a piston we can tell you how to convert it to a 115 bubble back since it'll be apart anyway.

I've seen folks bore out a V4 and a V6 crossflow to .064" over from standard thinking it'll make a huge difference. It never does. Start with the carbs and then let's look at overall performance. I'd almost bet the motor is running way too deep.

 

[jkrswld1]

Re: 1988 88hp spl conversion to 115

Thanks Guys
Don't have any horns going off. I don't believe shes running hot it does this even when you first start out if you idle any length of time. As far as running to deep I believe your right on the mark there. I've thought myself that it is setting to deep. I guess jack plate is in order. I'm gonna try rebuild on carbs first then if that doesn't work I'll move on to coils and power pack. What do you think?
Thanks Tim

 

[LubeDude]

Re: 1988 88hp spl conversion to 115

Sounds like you want to throw money at this engine hoping to get better performance. Trade it off and get at least a 150 on there and then start your set up. A brad new 115 would not make you any happier.

 

[jkrswld1]

Re: 1988 88hp spl conversion to 115

Thanks LD
Aye Aye Skipper I had just told my wife that same thing just before I read your post. It always helps to have an outside opinion when telling the wife you want to spend more money on something else haha!