crack in the block

[Kawboy]

I have a 1985 checkmate diplomat runabout, and I was told the block had a crack in it and I was wondering what kind of engine I could get to replace it or will I have to buy a new one just like it? The engine that is in it is a 1985 mercruiser 170.

 

[happy]

I'd do the glass work and put in a v-6

 

[Kawboy]

I was thinking I could replace with a regular chevy 350 but i wanted to make sure b4 i tried

 

[Kawboy]

wll all of the parts from my mercruiser 170 bolt to a 350 car engine?

 

[ezstriper]

A 170 is a specific merc block, very $$$$$$ and nothing will replace it as a direct bolt in..other engine will work but you will need everything to make it work...not for a novice changeover...Rob

 

[winter]

EZ speaks the truth. A conversion is a good deal of time and $$$. Figure going to a 350, you'll need to likely address the outdrive depending on what it hnging off the back. The fuel system is another issue. JB weld that crack, drive it and save up for a V8 checkmate

 

[Kawboy]

thnx for all the advise, Ill have to check to see what the lower unit is and let you know and mabe you could tell me which block I could go with because the water is pouring into the oil to bad to jb weld. I have plenty of experience with motors but only on vehicles, so changing the block wouldnt be that big of a problem.

 

[Diplomat82]

Maybe Big Dave will chime in. He has a Diplomat that he dropped a v8 into. He had to rework the mounts but I believe he was hitting 70mph on gps.

 

[Kawboy]

what di adjust valves on the engine mercruiser 170

 

[wca_tim]

I put a 383 in mine... and like it fine.

 

[Diplomat82]

A lot of good info on the 470 at Breezeworks

http://www.breezeworks.net/

 

[yellowfiero88]

I was thinking I could replace with a regular chevy 350 but i wanted to make sure b4 i tried

If your set on doing a V8 swap then do alot of research on it before jumping in. I would try to find a parts boat if you wanted to keep your boat. Mine came with a 260hp 350. I put a 350 truck motor in mine because they are 4 bolt mains. The difference is cam, brass freeze out plugs, and a windage tray from a stock automotive engine. The swap was bolt in since mine was setup already. The hardest part of my setup was setting the alignment of the motor for the driveshaft. You must have the tool to do it. If not aligned proper, you will chunk out the gimble in no time at all or tear apart the rubber piece where the drive shaft mounts to the engine(brain fart and cant remember the name of it). Also If you have a alpha it can handle the power as long as you dont build a huge SBC for it. One thing different on the outdrive is the gear ratio. V8 has a 1.5 ratio where as the 4 and 6 had a taller gear(not sure the ratios). This can be solved IMO by prop pitch selection.

Either way you go, stock or V8, it is not going to be cheap......... Bring Out Another Thousand.
Good luck

 

[wca_tim]

In all honesty, your conversion will be a pita compared to mine or big daves. You're going to have to build the engine mounts from scratch and get the alignment close enough on teh front mounts that you'll be able to adjust it correctly when done. In addition, with mine, I went from a 4.3 v-6 to a small block. It was a fairly tight fit but went and many of the parts bolted right up - you aren't going to have the benefit of having marine starter, alternator, water pump, etc, etc, etc... that'll bolt up. I would say the only way it might make sense is if you can find an entire marine 350 with everything to start with. And still, it's not going to be cheap - especially once you start adding in the unforseen "nickel and dime" stuff. You could probably buy another running boat for what it will cost you to shoehorn a 350 in there.

Might be best to see if you can get a replacement for what you have...

also, your outdrive gear ratio is probably a 1.98. I run a 1.81 with my smal block so I can run the kinds of props I wanted to. You will potentially be hard pressed to find props that are economical in the range you will need.

Finally, a small block will be realitively heavy in the back of your boat and you'll feel the difference. Mine would consistently run deep into the 50's with a 4.3 v6 (and break 60 lightly loaded on some days). if you run across a complete package for one of those you might consider that. gear ratio would be a lot closer too and make it easier to account for propping. You'll have the same potential issues here with building engine mounts, alignment, etc...

Note that if you do your own maint on a merc i/o, you should be removing the drive every year and carefully aligning it each and every time you reinstall it....