MerCruiser Altitude Conversion

[gordonandnicole]

I've just looked at used boat with a MerCruiser 4.3 190hp engine plus Alpha 1, but with the high altitude option. I live in Michigan. Is possible to convert this for use here without comprising too much of the performance? The boat is otherwise great and only 1 year old , but there's plenty of other boats around if it can't sensibly be done.

 

[FatBack]

Re: MerCruiser Altitude Conversion

new boat owner,<br /><br /> Take the boat on a test run. If it does what you want it to do--buy it. If it doesn't-- don't. You don't want to get a sour taste in your mouth right off the bat. Best of Luck

 

[Boatist]

Re: MerCruiser Altitude Conversion

New<br />I can not answer your question but the 190hp alpha 1 high altitude has 2.0 to 1 gear ratio and the standard Alpha 1 is 1.81 to 1. Your prop is going to turn a little slower about 10 percent. To change the gears back would cost way too much but may be ok by just useing a higher pitch prop. I guess I would at least check the pitch of current prop. If it is a 15 or 17 then at least you know 19 and 21 could be put on, but if it is already a 21 then to go to a higher pitch might be hard to find. At least to me seem easy to find props between 15 and 21 pitch.<br /><br />Welcome to the Board and the fun of boating.

 

[nickster]

Re: MerCruiser Altitude Conversion

New Boat Owner! I will agree with boatist that the gear ratio is different from one alttitude to another. I also think that the change the jetting in the carberator for the different alltitudes. I'm not real shure what you would have to do or if you would need to do anything to run this boat from high altitude to low altitude. But if you go from low altitude to high you have to change the gear ratio and the jetting in the carbs.

 

[Bondo]

Re: MerCruiser Altitude Conversion

Well, You guys are Pretty Close......<br />The V-6 motors come with the 1.65/1 ratio....<br />The V-8s come as 1.50/1....<br />The 1.84/1 ratio is for the I-6s,+ the 470s...<br />The 1.98/1 is for the I-4s.....<br />The High Altitude package amounts to a Drop of 1 step in outdrive gear ratio,+ Leanning of the fuel curve.....<br /><br />SO, You Should be looking at a 4.3l, with a 1.84/1 ratio,+ a very Lean running Carb....<br />You should be able to run this boat in Michigan by richening the fuel,+ stepping the prop pitch Up about 6"s....(Or regear the outdrive, It Costs about the Same, for the new gears, as the price of a new SS prop)<br />After-market props are ava. up to Atleast 32"s... So that's Not a problem....(I agree, Most props are in the 15", to 23" pitch range, but the After-market runs Much Higher #s)<br /><br />If you really Like this boat, Buy It..... <br />If it's just a boat that Almost Fits your Likes.... Let It Go....

 

[Boatist]

Re: MerCruiser Altitude Conversion

Bondo<br />Just wonder where you got your information. Info I gave is for the 2003 V6 4.3L 190 hp carb merc Alpha 1. His motor is a 2002 190 hp Alpha 1. Only 4.3L alpha 1 I see near 1.65 to 1 is the 4.3L MPI 220 hp motor and it is 1.62 to 1. also with my math looks like a 2 inch change in pitch.

 

[Boatist]

Re: MerCruiser Altitude Conversion

New Boat Onwer<br />Sorry I forgot to tell you about carb jets needing to be changed. It would run too lean if you did not change and that could burn a piston. Does not cost that much if you do your own work.